b gata h kei comes to mind. I hate ecchi, but this one was funny and I loved the female protagonist (most ecchi seem to have a really lame male protagonist surrounded by cliche girls who are one dimensional, but this one was different.)

I usually hate reverse harems as well and find them stupid, but kamigami no asobi was pretty good, which surprised me, especially since i hated utapri.

yowamushi pedal-I initially thought the art style was weird and expected it to be kinda boring. I couldn't have been more wrong.

Hunter X Hunter - Since this is action/adventure, and pretty popular, I thought it was gonna be like Naruto. But it's actually better in my opinion. It has lots of stuff Naruto doesn't have.

Free! - Since this is pretty much a sausage fest, I thought it was gonna be boring, but it's actually fun to watch them swim and compete. Although there are lots of fanservice for girls, I try my best to just focus on the story.

Nagi no Asukara - So in the beginning, they declare who likes who. So I thought this was gonna be one of those anime where ppl do some fucked up shits to each other to hook up with the one they like. But it's actually the opposite. And the story is really sad. And I like sad stuff.

Silver Spoon - This is one of those unpopular slice of life anime. Because basically, people think they are boring. But it's not when you get into it. This anime teaches you about life. This is one of the shows that made me chance my taste in anime. I actually prefer slice of life (probably the least popular genre) over action/adventure (the most popular genre) after watching this.

Love Live - Ok so when this aired, I wasn't very familiar with animes that aren't extremely mainstream. And then I started watching shitload of anime and started talking to other otakus. And a lot of otakus were talking about Love Live. At first, I thought it was for girls. Now I'm aware of how it has a huge fanbase of guys (Now I'm a huge fan myself)

RWBY - I went in to this show expecting to loathe it, regardless of how decent it could be, purely because making this show is a part of why Monty Oum hasn't worked on Dead Fantasy in years (I want that Namine fight!). And I just couldn't help but fall in love with it.

The original NGE and EoE movie are another one. When I both watched them the first time, I came away angry because I thought both of the endings sucked. I rewatched them both after another year or two, and paid more attention that time when watching them. It was then when I finally realized how much gold they both are.

I absolutely adore this anime now.
My first thoughts were that this anime is just another romance and it wasn't a big deal >_>
since I was all about "say I love you" at that time D; but man is this anime amazing.